WCDMA Receiver On-Chip Memory Reduction via Sliding Window
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Solution Overview
Problem
WCDMA receivers require significant on-chip memory for frame buffer storage due to the need for oversampling and storage of entire radio frames, leading to high storage demands without degrading the quality of received samples and maintaining receiver performance.
Innovation Solution
A system that includes a WCDMA receiver with an analog to digital converter, a sample rate converter, a digital to digital sigma-delta converter that reduces the number of bits in input samples, a memory unit for storing the reduced-bit samples, and a digital low pass filter to filter noise, allowing for decoding over an entire radio frame while minimizing memory requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If oversampling is used for granular delay search of multipath in the receiver, then measurement precision is improved, but device complexity increases due to enormous storage requirement
Solution Approach 1:
The patent extracts only the necessary information from the oversampled signal by using a sliding window approach that processes a limited number of recent samples (e.g., 16 samples) at a time, rather than storing and processing the entire oversampled frame. This allows granular delay search with high precision while maintaining minimal storage requirements in the buffer memory.
Solution Approach 2:
The patent performs preliminary processing of the oversampled signal by maintaining a sliding window buffer that continuously updates with new samples. This preliminary action prepares the data in a format ready for immediate delay search processing, eliminating the need to store and process the entire frame later, thus reducing storage complexity while preserving measurement precision.
2Reliability
If entire radio frame samples are stored for TFCI decoding, then reliability is improved, but device complexity increases due to large memory requirements
Solution Approach 1:
The patent extracts only the necessary portion of the radio frame samples needed for TFCI decoding by using a sliding window that maintains a limited number of recent samples. This extraction approach provides sufficient data for reliable TFCI decoding while avoiding the need to store the entire radio frame, thus reducing memory requirements and device complexity.
Solution Approach 2:
The patent implements a dynamic sliding window buffer that continuously adapts by adding new samples and removing old samples based on the processing needs. This dynamic approach ensures that the buffer always contains the most relevant data for TFCI decoding while maintaining a constant, manageable size, thereby balancing reliability with reduced memory requirements.
3Measurement precision
If high bit depth samples are used, then measurement precision is improved, but device complexity increases due to larger memory bandwidth and storage
Solution Approach 1:
The patent uses lower bit depth samples (e.g., 1-bit or low-resolution digital samples) in the sliding window buffer, which are essentially disposable representations that provide sufficient precision for the specific task of delay search and TFCI decoding. These simplified samples require minimal memory bandwidth and storage, yet maintain adequate signal quality for the intended processing operations.
Data Source
AI summary
A method of reducing an on-chip memory associated with storing frame buffer in WCDMA receiver includes obtaining, at a WCDMA front end receiver, an signal, transmitting, by an analog to digital convertor, input samples to a digital to digital sigma-delta converter, converting, by a sample rate convertor, a sampling rate associated with the input samples to a desired sampling rate for a rake receiver, quantizing, by the digital to digital sigma-delta converter, the input samples with a first number of bits to a converted data samples of a reduced number of bits, storing, at a memory unit, the converted data samples of the reduced number of bits, filtering the noise from the converted data samples to obtain a noise filtered converted data samples of the reduced number of bits, and decoding, at a WCDMA receiver processing unit, the noise filtered converted data samples over an entire radio frame.